diff --git a/src/builder/action.rs b/src/builder/action.rs
index 0f58738dbfd..40b67d427bb 100644
--- a/src/builder/action.rs
+++ b/src/builder/action.rs
@@ -70,6 +70,81 @@ pub enum ArgAction {
     /// assert_eq!(matches.get_many::<String>("flag").unwrap_or_default().count(), 0);
     /// ```
     IncOccurrence,
+    /// When encountered, act as if `"true"` was encountered on the command-line
+    ///
+    /// No value is allowed
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use clap::Command;
+    /// # use clap::Arg;
+    /// let cmd = Command::new("mycmd")
+    ///     .arg(
+    ///         Arg::new("flag")
+    ///             .long("flag")
+    ///             .action(clap::builder::ArgAction::SetTrue)
+    ///     );
+    ///
+    /// let matches = cmd.try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
+    /// assert!(matches.is_present("flag"));
+    /// assert_eq!(matches.occurrences_of("flag"), 0);
+    /// assert_eq!(
+    ///     matches.get_one::<bool>("flag").copied(),
+    ///     Some(true)
+    /// );
+    /// ```
+    SetTrue,
+    /// When encountered, act as if `"false"` was encountered on the command-line
+    ///
+    /// No value is allowed
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use clap::Command;
+    /// # use clap::Arg;
+    /// let cmd = Command::new("mycmd")
+    ///     .arg(
+    ///         Arg::new("flag")
+    ///             .long("flag")
+    ///             .action(clap::builder::ArgAction::SetFalse)
+    ///     );
+    ///
+    /// let matches = cmd.try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
+    /// assert!(matches.is_present("flag"));
+    /// assert_eq!(matches.occurrences_of("flag"), 0);
+    /// assert_eq!(
+    ///     matches.get_one::<bool>("flag").copied(),
+    ///     Some(false)
+    /// );
+    /// ```
+    SetFalse,
+    /// When encountered, increment a counter
+    ///
+    /// No value is allowed
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use clap::Command;
+    /// # use clap::Arg;
+    /// let cmd = Command::new("mycmd")
+    ///     .arg(
+    ///         Arg::new("flag")
+    ///             .long("flag")
+    ///             .action(clap::builder::ArgAction::Count)
+    ///     );
+    ///
+    /// let matches = cmd.try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
+    /// assert!(matches.is_present("flag"));
+    /// assert_eq!(matches.occurrences_of("flag"), 0);
+    /// assert_eq!(
+    ///     matches.get_one::<u64>("flag").copied(),
+    ///     Some(2)
+    /// );
+    /// ```
+    Count,
     /// When encountered, display [`Command::print_help`][super::App::print_help]
     ///
     /// Depending on the flag, [`Command::print_long_help`][super::App::print_long_help] may be shown
@@ -128,8 +203,40 @@ impl ArgAction {
         match self {
             Self::StoreValue => true,
             Self::IncOccurrence => false,
+            Self::SetTrue => false,
+            Self::SetFalse => false,
+            Self::Count => false,
             Self::Help => false,
             Self::Version => false,
         }
     }
+
+    pub(crate) fn default_value_parser(&self) -> Option<super::ValueParser> {
+        match self {
+            Self::StoreValue => None,
+            Self::IncOccurrence => None,
+            Self::SetTrue => Some(super::ValueParser::bool()),
+            Self::SetFalse => Some(super::ValueParser::bool()),
+            Self::Count => Some(crate::value_parser!(u64)),
+            Self::Help => None,
+            Self::Version => None,
+        }
+    }
+
+    #[cfg(debug_assertions)]
+    pub(crate) fn value_type_id(&self) -> Option<crate::parser::AnyValueId> {
+        use crate::parser::AnyValueId;
+
+        match self {
+            Self::StoreValue => None,
+            Self::IncOccurrence => None,
+            Self::SetTrue => Some(AnyValueId::of::<bool>()),
+            Self::SetFalse => Some(AnyValueId::of::<bool>()),
+            Self::Count => Some(AnyValueId::of::<CountType>()),
+            Self::Help => None,
+            Self::Version => None,
+        }
+    }
 }
+
+pub(crate) type CountType = u64;
diff --git a/src/builder/arg.rs b/src/builder/arg.rs
index d8892cef9d6..9f62e06241c 100644
--- a/src/builder/arg.rs
+++ b/src/builder/arg.rs
@@ -4900,7 +4900,9 @@ impl<'help> Arg<'help> {
         }
 
         if self.value_parser.is_none() {
-            if self.is_allow_invalid_utf8_set() {
+            if let Some(default) = self.action.as_ref().and_then(|a| a.default_value_parser()) {
+                self.value_parser = Some(default);
+            } else if self.is_allow_invalid_utf8_set() {
                 self.value_parser = Some(super::ValueParser::os_string());
             } else {
                 self.value_parser = Some(super::ValueParser::string());
diff --git a/src/builder/debug_asserts.rs b/src/builder/debug_asserts.rs
index 327887c4ed4..fd691c46760 100644
--- a/src/builder/debug_asserts.rs
+++ b/src/builder/debug_asserts.rs
@@ -649,6 +649,16 @@ fn assert_arg(arg: &Arg) {
         arg.name,
         arg.get_action()
     );
+    if let Some(action_type_id) = arg.get_action().value_type_id() {
+        assert_eq!(
+            action_type_id,
+            arg.get_value_parser().type_id(),
+            "Argument `{}`'s selected action {:?} contradicts `value_parser` ({:?})",
+            arg.name,
+            arg.get_action(),
+            arg.get_value_parser()
+        );
+    }
 
     if arg.get_value_hint() != ValueHint::Unknown {
         assert!(
diff --git a/src/builder/mod.rs b/src/builder/mod.rs
index 3c59b37350a..1f18ad51b0e 100644
--- a/src/builder/mod.rs
+++ b/src/builder/mod.rs
@@ -55,6 +55,7 @@ pub use command::App;
 #[cfg(feature = "regex")]
 pub use self::regex::RegexRef;
 
+pub(crate) use action::CountType;
 pub(crate) use arg::display_arg_val;
 pub(crate) use arg_predicate::ArgPredicate;
 pub(crate) use value_parser::ValueParserInner;
diff --git a/src/parser/parser.rs b/src/parser/parser.rs
index 61b17eacf13..c3a407f7e87 100644
--- a/src/parser/parser.rs
+++ b/src/parser/parser.rs
@@ -1182,6 +1182,67 @@ impl<'help, 'cmd> Parser<'help, 'cmd> {
                 matcher.add_index_to(&arg.id, self.cur_idx.get());
                 Ok(ParseResult::ValuesDone)
             }
+            ArgAction::SetTrue => {
+                let raw_vals = match raw_vals.len() {
+                    0 => {
+                        vec![OsString::from("true")]
+                    }
+                    1 => raw_vals,
+                    _ => {
+                        panic!(
+                            "Argument {:?} received too many values: {:?}",
+                            arg.id, raw_vals
+                        )
+                    }
+                };
+
+                matcher.remove(&arg.id);
+                self.start_custom_arg(matcher, arg, source);
+                self.push_arg_values(arg, raw_vals, matcher)?;
+                Ok(ParseResult::ValuesDone)
+            }
+            ArgAction::SetFalse => {
+                let raw_vals = match raw_vals.len() {
+                    0 => {
+                        vec![OsString::from("false")]
+                    }
+                    1 => raw_vals,
+                    _ => {
+                        panic!(
+                            "Argument {:?} received too many values: {:?}",
+                            arg.id, raw_vals
+                        )
+                    }
+                };
+
+                matcher.remove(&arg.id);
+                self.start_custom_arg(matcher, arg, source);
+                self.push_arg_values(arg, raw_vals, matcher)?;
+                Ok(ParseResult::ValuesDone)
+            }
+            ArgAction::Count => {
+                let raw_vals = match raw_vals.len() {
+                    0 => {
+                        let existing_value = *matcher
+                            .get_one::<crate::builder::CountType>(arg.get_id())
+                            .unwrap_or(&0);
+                        let next_value = existing_value + 1;
+                        vec![OsString::from(next_value.to_string())]
+                    }
+                    1 => raw_vals,
+                    _ => {
+                        panic!(
+                            "Argument {:?} received too many values: {:?}",
+                            arg.id, raw_vals
+                        )
+                    }
+                };
+
+                matcher.remove(&arg.id);
+                self.start_custom_arg(matcher, arg, source);
+                self.push_arg_values(arg, raw_vals, matcher)?;
+                Ok(ParseResult::ValuesDone)
+            }
             ArgAction::Help => {
                 debug_assert_eq!(raw_vals, Vec::<OsString>::new());
                 let use_long = match ident {
@@ -1278,6 +1339,15 @@ impl<'help, 'cmd> Parser<'help, 'cmd> {
                                 )?;
                             }
                         }
+                        ArgAction::SetTrue | ArgAction::SetFalse | ArgAction::Count => {
+                            let _ = self.react(
+                                None,
+                                ValueSource::EnvVariable,
+                                arg,
+                                vec![val.to_os_str().into_owned()],
+                                matcher,
+                            )?;
+                        }
                         // Early return on `Help` or `Version`.
                         ArgAction::Help | ArgAction::Version => {
                             let _ =
@@ -1294,12 +1364,7 @@ impl<'help, 'cmd> Parser<'help, 'cmd> {
     fn add_defaults(&self, matcher: &mut ArgMatcher) -> ClapResult<()> {
         debug!("Parser::add_defaults");
 
-        for arg in self.cmd.get_opts() {
-            debug!("Parser::add_defaults:iter:{}:", arg.name);
-            self.add_default_value(arg, matcher)?;
-        }
-
-        for arg in self.cmd.get_positionals() {
+        for arg in self.cmd.get_arguments() {
             debug!("Parser::add_defaults:iter:{}:", arg.name);
             self.add_default_value(arg, matcher)?;
         }
diff --git a/tests/builder/action.rs b/tests/builder/action.rs
new file mode 100644
index 00000000000..bdac85b7ddb
--- /dev/null
+++ b/tests/builder/action.rs
@@ -0,0 +1,347 @@
+#![allow(clippy::bool_assert_comparison)]
+
+use clap::builder::ArgAction;
+use clap::Arg;
+use clap::Command;
+
+#[test]
+fn set_true() {
+    let cmd =
+        Command::new("test").arg(Arg::new("mammal").long("mammal").action(ArgAction::SetTrue));
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(matches.get_one::<bool>("mammal"), None);
+    assert_eq!(matches.is_present("mammal"), false);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), None);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(2));
+}
+
+#[test]
+fn set_true_with_default_value() {
+    let cmd = Command::new("test").arg(
+        Arg::new("mammal")
+            .long("mammal")
+            .action(ArgAction::SetTrue)
+            .default_value("false"),
+    );
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+}
+
+#[test]
+fn set_true_with_default_value_if_present() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::SetTrue)
+                .default_value_if("dog", None, Some("true")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::SetTrue));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("dog").unwrap(), true);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<bool>("dog"), None);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+}
+
+#[test]
+fn set_true_with_default_value_if_value() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::SetTrue)
+                .default_value_if("dog", Some("true"), Some("true")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::SetTrue));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("dog").unwrap(), true);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<bool>("dog"), None);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+}
+
+#[test]
+fn set_true_with_required_if_eq() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::SetTrue)
+                .required_if_eq("dog", "true"),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::SetTrue));
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<u64>("dog"), None);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+
+    cmd.clone()
+        .try_get_matches_from(["test", "--dog"])
+        .unwrap_err();
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--dog", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("dog").unwrap(), true);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+}
+
+#[test]
+fn set_false() {
+    let cmd = Command::new("test").arg(
+        Arg::new("mammal")
+            .long("mammal")
+            .action(ArgAction::SetFalse),
+    );
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(matches.get_one::<bool>("mammal"), None);
+    assert_eq!(matches.is_present("mammal"), false);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), None);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(2));
+}
+
+#[test]
+fn set_false_with_default_value() {
+    let cmd = Command::new("test").arg(
+        Arg::new("mammal")
+            .long("mammal")
+            .action(ArgAction::SetFalse)
+            .default_value("true"),
+    );
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), true);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+}
+
+#[test]
+fn set_false_with_default_value_if_present() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::SetFalse)
+                .default_value_if("dog", None, Some("false")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::SetFalse));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("dog").unwrap(), false);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<bool>("dog"), None);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+}
+
+#[test]
+fn set_false_with_default_value_if_value() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::SetFalse)
+                .default_value_if("dog", Some("false"), Some("false")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::SetFalse));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<bool>("dog").unwrap(), false);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<bool>("dog"), None);
+    assert_eq!(*matches.get_one::<bool>("mammal").unwrap(), false);
+}
+
+#[test]
+fn count() {
+    let cmd = Command::new("test").arg(Arg::new("mammal").long("mammal").action(ArgAction::Count));
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(matches.get_one::<u64>("mammal"), None);
+    assert_eq!(matches.is_present("mammal"), false);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), None);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 1);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 2);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(2));
+}
+
+#[test]
+fn count_with_default_value() {
+    let cmd = Command::new("test").arg(
+        Arg::new("mammal")
+            .long("mammal")
+            .action(ArgAction::Count)
+            .default_value("10"),
+    );
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 1);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+
+    let matches = cmd.clone().try_get_matches_from(["test"]).unwrap();
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 10);
+    assert_eq!(matches.is_present("mammal"), true);
+    assert_eq!(matches.occurrences_of("mammal"), 0);
+    assert_eq!(matches.index_of("mammal"), Some(1));
+}
+
+#[test]
+fn count_with_default_value_if_present() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::Count)
+                .default_value_if("dog", None, Some("10")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::Count));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<u64>("dog").unwrap(), 1);
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 10);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<u64>("dog"), None);
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 1);
+}
+
+#[test]
+fn count_with_default_value_if_value() {
+    let cmd = Command::new("test")
+        .arg(
+            Arg::new("mammal")
+                .long("mammal")
+                .action(ArgAction::Count)
+                .default_value_if("dog", Some("2"), Some("10")),
+        )
+        .arg(Arg::new("dog").long("dog").action(ArgAction::Count));
+
+    let matches = cmd.clone().try_get_matches_from(["test", "--dog"]).unwrap();
+    assert_eq!(*matches.get_one::<u64>("dog").unwrap(), 1);
+    assert_eq!(matches.get_one::<u64>("mammal"), None);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--dog", "--dog"])
+        .unwrap();
+    assert_eq!(*matches.get_one::<u64>("dog").unwrap(), 2);
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 10);
+
+    let matches = cmd
+        .clone()
+        .try_get_matches_from(["test", "--mammal"])
+        .unwrap();
+    assert_eq!(matches.get_one::<u64>("dog"), None);
+    assert_eq!(*matches.get_one::<u64>("mammal").unwrap(), 1);
+}
diff --git a/tests/builder/main.rs b/tests/builder/main.rs
index 124111f1011..b034bba7af7 100644
--- a/tests/builder/main.rs
+++ b/tests/builder/main.rs
@@ -1,3 +1,4 @@
+mod action;
 mod app_from_crate;
 mod app_settings;
 mod arg_aliases;